Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

927
FXUS63 KLOT 300541
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1241 AM CDT Mon Mar 30 2026

.KEY MESSAGES...

- Heightened brush and grass fire weather threat through this
  evening

- Storm system to bring chances for showers and thunderstorms
  late Monday night through Tuesday. A few storms could be
  strong to severe, especially Tuesday afternoon/evening.

- Stormy weather pattern expected to persist into next weekend.

&&

.DISCUSSION...
Issued at 248 PM CDT Sun Mar 29 2026

Through Monday:

Breezy southwesterly winds prevail this afternoon. Wind gusts
have been steadily between 20 and 25 mph, though isolated gusts
to 30 mph are possible prior to sunset. Relative humidity values
have dropped into the 20-30 percent range. With these dry
conditions present, there remains a heightened threat of brush
and grass fires this afternoon and early evening. Winds are
expected to diminish after sunset down to around 5 to 10 mph.

There is a weak mid level wave that will pass over central
Illinois this evening. High res guidance has a weak vort lobe
associated with this wave. It would not be surprising if there
were a few returns that show up on radar, but with the amount of
dry air present in the low levels, no precipitation is
expected. As this wave exits early tomorrow morning, cloud cover
should diminish toward daybreak.

An upper level long wave trough is expected to eject out of
British Columbia overnight and move across the northern Plains
on Monday. Meanwhile, a mid level shortwave trough is projected
to eject out of the Colorado front range and move east through
the day. Neither of these waves will provide precipitation
chances for the area until Monday evening (more on that in the
discussion below). A warm front out ahead of the midlevel trough
will extend into Illinois and lift northward through the day.
Winds will remain southwesterly, providing stronger warm air
advection aloft, increasing 850 mb temps to around 15C. Surface
temperatures are expected to increase to around 70F along the
lakeshore and well into the 70s for the rest of the area
(possibly near 80 the closer to west-central Illinois). High res
guidance continues to show a pseudo-lake breeze, if not a back
door front entirely, develop late tomorrow afternoon. Depending
on the timing of it, this may impact overall high temperatures
forecasted in Lake County Illinois and down to the city of
Chicago, which may result in high temperatures being observed
around the lunch hour, and then steadily falling into the
evening.

DK

Monday Night through Sunday:

The main forecast focus is on potential convective trends and
unseasonable warmth Monday night through Tuesday evening and then
a likely rainy and blustery stretch late Wednesday through
Thursday evening.

On Monday evening, a warm front will be north of most of the area,
with the possible exception of portions of the Illinois lakeshore
(most likely near and north of downtown Chicago). Here, the front
may have sagged back south due to lake breeze enhancement,
resulting in cooler conditions into the evening. With weak surface
low pressure over southwest or southern Wisconsin, pressure falls
should result in the lake reinforced front retreating back north
by the late evening (assuming it makes inroads into NE IL Mon PM).
This will be followed by increasing and at times gusty southwesterly
winds overnight, with unseasonably mild temps in the 60s.

Regarding convective potential, another impressive EML plume will
overspread the region, though initial antecedent dry low to mid
levels will result in strong capping. A majority of the available
guidance holds the capping through much of if not the entire night.
Skeptical of any activity during the evening hours when the
capping will be at its strongest. Overnight, most of the large
scale forcing (500 mb up to jet level) will be well to our north.
A 700 mb impulse crossing Iowa will result in increased mid-level
moisture. However, with an overall lack of stronger forcing, it`s
unclear if isentropic lift from a robust low-level jet will be
able to moisten up to the base of the cap to effectively tap into
the modeled MUCAPE reservoir. It`s also possible that the 700 mb
wave is slow enough for any storms within the area to hold off
until towards or beyond daybreak Tuesday.

With the above considerations in mind, capped maximum PoPs in the
chance range near and north of I-80, highest at ~40-50% near and
northwest of a Peru IL to Evanston line. The GFS and RRFS appeared
to be too convectively active given the modest overall forcing.
If the capping isn`t breached, there`s a play for primarily dry
conditions through the night areawide. On the other hand, if any
storms do occur, the very steep mid-level lapse rates may yield a
threat for isolated severe hail and gusty winds, particularly
amidst sufficiently supportive effective bulk shear (which is also
uncertain). SPC`s day 2 update maintained a 1/5 threat level
(marginal risk) north of I-80, reasonable for now.

Tuesday`s specific details are muddy at best due to continued
modest/subtle/unclear forcing mechanisms until later in the day.
Convective chances Tuesday morning, as alluded to earlier, may be
tied to the aforementioned 700 mb impulse crossing the MS River
and sufficient erosion of the lingering capping. Didn`t have
enough confidence for any notable changes to PoPs Tuesday morning
through midday, and thunderstorm mention above slight chance/isolated.
A cold front trailing from low pressure tracking towards Lake Huron
and modest height falls should be able to touch off showers and at
least scattered thunderstorms sometime during the PM hours, though
there`s also a good deal of uncertainty on timing specifics
(afternoon vs. primarily towards and during the evening).
Undoubtedly, prior convection in the morning, or a lack thereof,
can be expected to modulate the afternoon and evening showers and
storms. Outside of the highly uncertain convective forecast,
Tuesday will feature unseasonable warmth and southwest winds
gusting up to 30-40 mph. The extent to which official forecast
highs in the mid to upper 70s north of I-80 and upper 70s to
around 80 south of I-80 are realized will also be tied to shower
and t-storm, and cloud cover trends.

Where temperatures end up will determine how much instability can
be realized during and just after peak heating, pertinent to the
threat for strong to severe storms. Still steep mid-level lapse
rates (but not quite as steep as earlier in the day) and 30-50 kt
of deep layer shear (unidirectional shear profile) may be
supportive of isolated large hail and wind damage with any more
intense storms. It does appear that veering southwesterly winds
and fairly large temperature-dew point spreads should tend to
limit a tornado threat.

The front will sweep across the area Tuesday night, shifting
thunderstorm potential south of the area and bringing notably
cooler conditions on Wednesday. Any break in the rain will be
short-lived, especially with southward extent. Guidance has come
into better agreement on widespread showers late Wednesday through
Thursday, likely accompanied by some threat for storms as well.
This period will need to be watched for corridors of heavy
rainfall and some associated threat for flooding. Blustery
northeast winds will make for a raw day areawide, particularly
lakeside, on Wednesday. On Thursday, the exact path of surface
low pressure will determine how far north a warm front can lift
north, bringing temps back into the 60s (possibly even supporting
a surface based severe threat). North of the boundary, northeast
winds will continue to result in much cooler conditions (40s and
50s).

In the wake of the Thursday evening/night cold front passage,
Friday should dry out for much of the area. Another round of
showers and some thunderstorms then appears probable sometime in
the Friday night through Saturday timeframe. At this time, next
Sunday, Easter Sunday for those celebrating, appears that it
should be quieter and cooler.

Castro

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1241 AM CDT Mon Mar 30 2026

Key messages:

- Gusty south-southeast winds of 20-25 kt expected this
  afternoon into this evening.

- Period of LLWS likely (60%+ chance) mid to late this evening
  through early Tuesday morning.

- Low, but non-zero threat of thunderstorms after midnight
  tonight (Monday night).

Light south-southwesterly winds early this morning will pick up
and turn gusty up to 20 to 25 kt again for this afternoon. While
surface gusts may become more sporadic for period after sunset
early this evening, it does appear we may continue to have
at least some periodic gustiness to the winds tonight. However,
of more concern is the increased threat for a few hour period
of LLWS mid to late this evening through early Tuesday morning
as a southwesterly low-level jet quickly intensifies.
Considering peak speeds within this low-level jet could reach
55-60 kt at only about 2,000 ft AGL late this evening, we have
opted to include a formal mention of LLWS in the TAFs after 02Z
this evening. It appears this threat should wane prior to
daybreak Tuesday morning.

The other forecast element we will be monitoring for the area
is the threat for some showers and thunderstorms tonight
(Monday night) and on Tuesday. While the highest potential for
thunderstorms impacting the terminals looks to be with a cold
frontal passage Tuesday afternoon and evening, there is also a
low (20-30%) chance for a few scattered showers and storms ahead
of the system late tonight (after 06Z Tuesday) into Tuesday
morning. However, due to the low chance (and confidence) of
these potential storms impacting a given terminal, no formal
mention has been included in the TAFs at this time.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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